SNK Neo Geo NEO-MVH six slot board repair

Just finished the arduous task of replacing all the capacitors on the board out of my office’s SNK Neo Geo MVS-6-25 cabinet. It’s a monster, roughly 16″x20″ and two boards stacked one on top of another. The top board is identified as NEO-MVH SLOT6, while the bottom is labeled with NEO-MVH MV6.

This monster board has a monster cap list, with a total of 39 capacitors required to totally fill it out. Thankfully they’re all labeled on board with which values go where (though voltages are NOT labeled so keep track!) The condensed list of everything I had to order is as follows:

3x  1.0μF  50v
12x 4.7μF  25v
2x  4.7μF  50v
1x  10μF   16v
3x  22μF   16v
1x  22μF   50v
1x  47μF   16v
5x  100μF  50v
2x  220μF  16v
1x  220μF  35v
6x  470μF  16v
2x  1000μF 16v

I didn’t follow my advice and failed to note what exact voltages went where, but kinda felt it out based on the quantities and locations… Risky, but it worked. I fired the board up to test and the newly potent audio circuits startled the hell out of me since I’d left the volume slider at close to maximum from its previous weakened state.

While working it over I noticed that a few caps have incorrect labels screened on the board. In particular there’s a pair of 4.7μF caps with 4.7K screened at their position as though they were resistors.

Also ran a set of leads from the old battery location so I can locate a new rechargeable battery offboard once I source one.

We got the power

The Neo Geo I picked up on Saturday came with a handful of relatively minor issues. Among them was a noisy power supply fan that quieted down after a few minutes of operation. Fine if it’s living in a basement arcade, not so much in an office, so it was one of the first things I wanted to fix.

The power supply in the Neo Geo (an MVS-6-25 oversize upright unit) is a Happ Controls Power Pro. It’s extremely easy to extricate, held in by four screws and hooked up to the rest of the machine but three modular connectors. Once you’ve got it out there’s a handful of standard computer case screws to remove and you’ve got it open.

Roomy inside, and we can see that the fan used is the same style found in pretty much every desktop computer ever.

The spare I had on hand was a new Rosewill unit from Newegg, and it had an extra lead for speed monitoring. The one in the power supply had a 2 pin connector so I needed to splice on the old connector to the new fan for it to work. Couple minutes spent soldering and some heat shrink tubing and the operation was complete.

Everything stitched back together. Overall a very simple repair, but it will make the machine way more pleasant to be around. As a bonus I found an original SNK mini marquee blanking plate and a few dollars worth of quarters under the power supply when I pulled it. Yay!